Highway signs are usually susceptible to damage or destruction when struck by a vehicle and are usually of metal which may inflict comparable damage on the striking vehicle. Straightening of the post is usually uneconomical and costly replacement is the usual remedy.
Either in a highway or sporting context, the information provided by the sign after it has been knocked down or broken by impact is no longer available and this usually constitutes a substantial safety hazard.
Slalom ski gates currently available are generally rigid poles made of bamboo or other lightweight substances which will break or easily be uprooted from the snow upon impact so as not to harm the skier. These uprooted poles and fragments constitute a hazard to other skiers and necessitate a system of constant vigilence and replacement which is costly as well as dangerous.
In an attempt to obviate the need for complete replacement and to reduce the damage to both the post and the body impacting the post, a number of structures have been proposed which break over or yield upon impact. Several types of delineator posts have been tried which have frangible sections which sheer away under impact, however, such devices still do not avoid or overcome the need for replacement but merely are helpful in reducing the damage sustained by the vehicle striking the delineator post.